Conditions for the formation of bityrosine cross-linkages between muscle proteins in model systems and between lens proteins in intact lenses will be defined more fully. This will include the spatial requirement, the role of small molecules such as tyrosine and ascorbic acid and the effectiveness of various wave-lengths of irradiating light. In addition, we plan to determine the protein sulfhydryl group distribution and state of oxidation in a large number of single cataractous lenses.